Análises fisiológicas e bioquímicas de Cyathula prostrata (L.) blume atacada por Herpetogramma bipunctalis

Abstract

The insect Herpetogramma bipunctalis Fabricius (1974) (Crambidae) is a pest that occurs in North America and South America, being found in Brazil attacking crops of commercial interest. The species Cyathula prostrata (L) Blume (Amaratheceae) is a plant native to tropical Africa and Asia, and is also found in Brazil. This plant exhibits pharmacological and medicinal properties and has been used in folk medicine. The insect H. bipunctalis feeds on the leaves of C. prostrata. The objective of this study was to study plant-insect interaction, considering biochemical and physiological aspects to develop strategies to control insects that damage plants of commercial interest. In this work, it was performed physiological (gas exchange parameters and chlorophyll a fluorescence) and biochemical (oxidative stress) analyzes of leaves of C. prostrata submitted to the attack of H. bipunctalis caterpillars at different times of exposure to the insect. The gas exchange parameters were: photosynthetic rate (A), stomatal conductance (gs), internal carbon concentration (Ci) and transpiration (E) and chlorophyll a fluorescence parameters: maximum fluorescence (Fm), maximum quantum efficiency of PSII (ΦPSII), electron transport rate (ETR), photochemical dissipation coefficient (qp), and oxidative stress enzymes were altered in plants of C. prostrata submitted to the attack of H. bipunctalis caterpillars at times of 12, 36 and 60 hours. The herbivory of the insect H. bipunctalis decreased the photosynthetic capacity of undamaged and damaged leaves of C. prostrata reducing the parameters of gas exchange (A, gs, E) and promoting increase in (Ci). Reductions in the fluorescence parameters of chlorophyll a (Fm, Fv / Fm, ΦPSII, ETR and qp) were observed. There was also a significant increase in the concentration of hydrogen peroxide (H2O2) in damaged leaves at 12h (4,8%), 36h (59,4%) e 60h (66,9%) and a significant increase of malonic aldehyde (MDA) at 60h (69,2%) in damaged leaves, suggesting the occurrence of oxidative stress. Collectively, the obtained data indicate that biotic stress interferes with the physiology of C. prostrata. The presented data suggest that the effect of the reduction in the leaf area caused by the herbivory of the insect H. bipunctalis, reduced the investment in photosynthesis for the plant to invest in defense related metabolism.